A pilot ignited engine operates on two fuels concurrently, a main fuel primarily responsible for producing torque and a pilot fuel primarily responsible for igniting the main fuel. Because the pilot fuel is intended primarily to ignite the main fuel, the torque produced by the pilot fuel is generally very small in comparison to the torque produced by the main fuel. Combustion of the pilot fuel raises the pressure and temperature within the combustion chamber to an ignition threshold of the main fuel. Once the ignition threshold is reached, the main fuel begins to combust. The amount and the timing at which the pilot fuel is introduced into the combustion chamber are precisely metered to achieve the ignition threshold at a specified time in relation to the combustion cycle. The timing of the main fuel is not as closely controlled. In an engine that uses a gas mixer in the intake to meter the main fuel, transport delays between a fueling change at the gas mixer and the fueling change being realized as a change in engine torque result in slow engine response to changes that affect engine fueling requirements, such as changes in speed or engine loading.
Therefore, there is a need in pilot ignited engines to improve responsiveness to changes that affect engine fueling requirements.